Patent GB-826045-A (GB)
Title: Multiplex telegraph receiver
IPC: H04L7/033
Filed: 1956-11-06
Abstract: 826,045. Multiplex telegraphy. TELETYPE CORPORATION. Nov. 6, 1956 [Dec. 28, 1955], No. 33850/56. Class 40 (3). [Also in Group XL (c)] In a multiplex telegraph receiver an arrangement for synchronizing the operation of animpulse distributer, driven by a train of pulses supplied by a constant-frequency source, with the times of arrival of the telegraph signal impulses by subtracting pulses from, or adding pulses to, the train of drive pulses without altering the frequency of the pulse source, the impulse distributer, comprising a plurality of stages which are successively operated at signal impulse frequency, is driven by the train of drive pulses through a cyclically-operating frequency divider of the closed-ring type having a plurality of successively operated component stages and performing a complete cycle of operation at signal impulse frequency, during which frequency divider cycle the operation of a particular one of its stages serves to advance the operative stage of the distributer and in which control pulses derived from the received signal pulses are compared in two sets of coincidence gates with comparison pulses applied to the individual gates of one set by the operation of different stages of the frequency divider which are operated during a portion of the frequency divider cycle occurring just after the particular one stage has been operated and with comparison pulses applied to the individual gates of the other set by the operation of different stages of the frequency divider which was operated during a portion of the frequency divider cycle occurring just before the particular one stage is operated, so that an output utilized to subtract pulses from the train of drive pulses is obtained from one or more of the gates of said one set when the times of arrival of the signal impulses lag slightly behind the operation of the corresponding distributer stages, and an output utilized to add pulses to the train of drive pulses is obtained from one or more gates of the other set when the times of arrival of the signal pulses are slightly in advance of the operation of the corresponding impulse distributer stages. The incoming pulses received at 10, Fig. 4, are applied to a gate comprising input rectifier 11 and rectifiers 12, 13 which receive positive sampling pulses over conductors 109, 112 for a short period at the centre of the element period. If the received element is a mark, the gate passes a positive pulse over conductor 16 to a matrix 17, Fig. 1, comprising twenty-four diode gates, such as that indicated at 58, arranged in four columns of six gates. The four columns are associated with the multiplex channels A, B, C and D, and the six gates in a column pertain to the elements of a code signal comprising five information elements and a sixth operating element, normally a mark. The column gates are controlled by a distributer 26 comprising transistors 26a ... 26f with a normally-conducting control transistor 106 so that during a cycle of the distributer, the transistors 26a ... 26f conduct in sequence and sequentially but off transistors 38 to apply positive pulses to associated conductors 41 ... 46 connected to the four gates in each row. The channel, or vertical row of gates, is selected by a distributer 27 comprising four normally non-conducting transistors 27a ... 27d under control of a normally conducting transistor 37. The sequential conduction of the transistors 27a ... 27d renders the transistors 48 conductive in turn to pass positive pulses to the conductors 51 ... 54 linked respectively to the four columns of diode gates connected by cables 21 ... 24 to the receivers fed by the multiplex. The operating pulses for the system are derived from a crystal oscillator 66, Fig. 5, coupled to a fourfold division circuit 67 operating a transistor 76 to non-conduction to provide pulses to a transistor 86, Fig. 3, associated with a threefold division circuit 88 comprising transistors 88a ... 88c. The diode 69 of junction 73, Fig. 5, connected to transistor 67a is normally held positive by normally conducting transistor 72, and at gate point 82 associated with transistor 67c, a negative potential is applied from normally conducting transistor 81. Circuit 88, Fig. 3, operates normally conducting transistor 93 of a fivefold division circuit comprising transistors 94a ... 94e which on the operation of transistor 94c passes a positive pulse to diode 96, conductor 97 and resonant circuit 98 to normally conducting transistor 99 controlling a seven-stage division circuit 101 comprising normally non-conducting transistors 101a ... 101g. When transistor 101a conducts, a positive pulse is applied over diodes 102, 103 to a normally conducting transistor 106 which controls the impulse distributer 26. A positive pulse taken from the transistor 101d when it conducts, renders transistor 111 non-conducting to pass a positive pulse over conductor 112 for a short period at the centre of the element period, and a positive pulse at the centre of this short period is generated over conductor 109 when transistor 108 is rendered non-conducting by the conducting condition of the transistor 94c. Synchronism control arrangement.-The operation of the synchronizing arrangement is determined by comparing the transisitions of mark to space on the incoming line 10 with the operation of the transistors of the frequency-dividing chain 101, transitions occurring when the transistors 101b, 101c or 101d are in conductive condition indicating that the distributer is in advance of the signals, whilst conduction of 101e, 101f or 101g at the transition time is indicative of a lagging condition of the distributer. The change from space to mark on the line 10 is impressed on line 114 via capacitor 116 and a diode and changes over a one-shot multivibrator 119 having a pulse period equal to that of the conducting period of a transistor 101a ... 101g of the chain 101. A positive pulse is passed over conductor 122 to junction points 131, 132, 133 and 141, 142, 143. If transistor 101b, 101c or 101d is conducting, a pulse is passed over conductor 126, 127 or 128 and a positive pulse is fed over conductor 144 to a bi-stable circuit 149. If, however, 101e, 101 f or 101g is conducting, a positive pulse is fed over conductors 136, 137, 138 and a positive pulse passes over conductor 146 to the bi-stable circuit 189. In the former case, the circuit 149 changes over, and a positive pulse received from differentiating capacitor 151 is blocked by diode 152. Each time channel B is selected by the distributer 27, a pulse is passed over conductor 52 and via conductor 153, Fig. 4, to a normally conducting transistor 156 which becomes non-conductive for a short period, and again conducting to produce from differentiating capacitor 163 a negative pulse which over diode 164 charges capacitor 166 negatively. The negative pulse also renders transistor 157 conductive to lower the potential of capacitor 163. Subsequent negative pulses to the capacitor 163 effect further negative charging of capacitor 166 until a bi-stable circuit 169 is changed over and transistors 160, 161 are also changed to the conductive condition to discharge the capacitor 166. A negative pulse on conductor 171 is without effect since transistor 148 is already conducting. The next positive pulse over conductor 153 passes via diodes 174, 176 and makes transistor 158 non-conducting so that a positive pulse is now passed over conductor 171 to make transistor 148 of circuit 149 non-conducting with the result that a negative pulse is passed by capacitor 151 and diode 152 to change over one-shot multivibrator 181 so that transistor 72 passes a negative pulse from its collector eleetrode to the gate position 73. The time duration of the pulse from circuit 181 is normally one cycle of the chain 67 so that a pulse to transistor 76 is suppressed and the distributer retarded. The retarding process is continued until any change from space to mark occurs during the period of conduction of the transistor 101a. In a generally similar manner, when the distributer is running slowly, the pulse over conductor 146 changes over bi-stable circuit 189 to produce at differentiating capacitor 191 a negative pulse which is blocked by diode 192. When subsequently this positive pulse is applied over conductor 171 transistor 188 is made non-conducting and transistor 187 conducts thereby passing a positive pulse to transistor 194 of a one-shot multivibrator 196 producing from its collector electrode a positive pulse which is applied to gating point 82 so that a pulse is fed also from transistor 67c and the transistor 76 receives an additional operating pulse to speed up the distributer. The capacitors 182, 197 of the vibrator circuits 181, 196 may be such as to allow the pulses to extend over a number of cycles of the dividing chain 67. Also, the switch S, Fig. 4, may be operated to connect a capacitor, such as 166, of a different value, or to allow of operation of the circuit 169 by successive pulses over the conductor 153. At the commencement of operation the arrangement is brought into correct phase operation by transmission of a test signal over channel B to a printer connected to cable 22 and a push-button switch 201, Fig. 4, is continuously operated until the signal is correctly received. The actuation of switch 201 energizes a relay 202 which at contact member 203 disconnects the capacitor 166. The pulse from conductor 52 is also fed over conductor 207, diode 208 to a transistor 209 producing a pulse which is applied to the bi-stable trigger 214 passing a positive pulse over conductor 216, closed contact member 204, conductor 217 and diode 218 to the gate junction 221 so that the transistor 106 is operated by additional pulses to step forward the distributer. The closure of contact member 206 connects a capacitor 222, Fig. 5, in parallel with the capacitor 197 so